tetrahydrides

Tetrahydride is a term used for chemical compounds in which four hydrogen atoms are bound to a central element or metal center. The class includes molecular hydrides of main-group elements such as methane (CH4), silane (SiH4), germane (GeH4) and stannane (SnH4), as well as metal tetrahydrides described in inorganic and organometallic chemistry.

In most molecular tetrahydrides the central atom is surrounded by four hydrogen atoms in a tetrahedral arrangement, corresponding to an AX4 skeleton. Bonds are covalent sigma bonds, and the four X-H bonds contribute to a nonpolar or weakly polar molecule depending on the central atom. CH4 is highly symmetric and nonpolar; heavier examples remain tetrahedral but with differing bond strengths and reactivity.

Methane CH4 is a major component of natural gas and is relatively inert under ordinary conditions. Silane SiH4 and germane GeH4 are gaseous at room temperature and widely studied as precursors for deposition processes in the semiconductor industry. Stannane SnH4 is less stable and is typically prepared and studied under controlled conditions; heavier tetrahydrides tend to be unstable or exist only as transient species.

Most tetrahydrides are formed by direct combination of the element with hydrogen or by hydride transfer reactions. They can be sensitive to air and moisture; hydrolysis of SiH4 yields silica and hydrogen gas. Some tetrahydrides, particularly transition metal derivatives such as TiH4, exist as volatile species at low temperatures and require inert conditions to handle.

These compounds play roles as gas-phase reagents, starting materials for thin-film deposition, and in studies of fundamental bond formation to hydrogen. Methane is a fuel and feedstock; silane and germane are used in chemical vapor deposition to produce silicon- and germanium-containing films.